The present disclosure relates to systems and methods for treating subterranean formations. In particular, the present disclosure relates to conformance gels or sealants that may be used to prevent the water from coming to the surface or otherwise interfering with the production of hydrocarbons.
Natural resources such as oil or gas residing in a subterranean formation can be recovered by drilling a wellbore that penetrates the formation. As used herein, the term “formation” refers to a region having similar geological characteristics, including the presence of particular formation fluids. The wellbore passes through a variety of subterranean formations. This may include reservoir zones (i.e., formations that contain oil or gas) and non-reservoir zones (i.e., formations that do not contain oil and gas). In some situations, non-reservoir zones may contain water instead of oil and gas.
After the wellbore has been drilled, the well is completed. The completion process includes the steps of preparing the drilled wellbore for the production of hydrocarbons. The completion process may include, for example, inserting production tubing into the wellbore, perforating the production tubing, stimulating the reservoir zones (e.g., acidizing or fracturing), etc. In general, a goal of the completion process may be to fluidly connect the wellbore to the reservoir zones (to allow hydrocarbons, such as oil and gas, to be produced) while isolating the wellbore from the non-reservoir zones (to prevent non-hydrocarbon formation fluids, such as water, from being produced). After a well has been completed, it may produce hydrocarbons for a period of months or even years.
While a well remains in production, the formation fluids in the reservoir zones may change over time. For example, the permeability of various zones in the formation may vary considerably. Over time, the hydrocarbon may be produced from higher permeability zones sooner than from lower permeability zones, and the high permeability zones may then begin to produce water. If a well begins producing water, it may be remediated by sealing off the water-producing zones. One way to remediate a water-producing well involves pumping a polymer gel down the wellbore into the water-producing zone. The gel seals the water-producing zone, creating a barrier that prevents the water in the formation from flowing into the wellbore. The remaining hydrocarbon-producing zones continue to produce oil and gas that can be recovered from the well.
The polymer gels may include an additional crosslinking agent, such as a metal crosslinker, that increases the strength of the gel by causing the polymer chains to crosslink together. The increased gel strength generally allows the gel to function more effectively and last longer. However, in certain circumstances, the crosslinking agent may cause the gel to over-crosslink. Over-crosslinking essentially causes the gel to collapse on itself and squeeze water out of the gel. This loss of water is known as syneresis and causes the volume of the gel to shrink. As the gel shrinks, it loses its ability to seal the water-producing zone and may even be washed out of the well.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.